D.C. Del. Walter E. Fauntroy and two other black leaders were arrested inside the South African embassy last night after staging a sit-in to try to win the release of black South African labor leaders who have been jailed without any charges being placed against them.

Uniformed officers of the Secret Service handcuffed Fauntroy, U.S. Civil Rights Commission member Mary Frances Berry and Randall Robinson, executive director of TransAfrica, a black foreign policy lobbying group, after their arrests. Then they escorted them to waiting cars and drove them to a D.C. police substation in Northwest Washington.

The three were charged with unlawful entry of an embassy, a misdemeanor that can draw a penalty of up to six months in jail and a $100 fine.

D.C. police told the protesters they could be released immediately after they had been charged, but all refused and insisted that they be held overnight to await a D.C. Superior Court hearing this morning. Fauntroy and Robinson were held in the police department's central cellblock, while Berry was taken to the D.C. Jail.

Fauntroy, Berry, Robinson and a fourth person -- Eleanor Holmes Norton, a former chairman of the Equal Employment Opportunity Commission and now a Georgetown University law professor -- had gone to the South African embassy to discuss current racial and labor unrest in South Africa with Ambassador Bernardus G. Fourie and two of his aides.

An hour after the meeting started, Norton left the embassy at 3051 Massachusetts Ave. NW and told about 30 demonstrators outside that Fauntroy, Berry and Robinson intended to sit in at the embassy until their demands for the release of nine jailed South African labor leaders were met.

The embassy said it learned of the group's intentions when news reporters called about the protest. Embassy spokesman Pieter Swanepoel said Fourie immediately ended the discussions about South African policies, and asked Fauntroy, Berry and Robinson to leave, but that they refused.

"The police were then asked to remove them from the premises," Swanepoel said.

Norton said the arrests "were exactly what we thought would happen. What can we do except draw the attention of the world to black South Africans who cannot speak for themselves?"

"Our own government is no recourse for us at this point," Norton added. She said the Reagan administration's policy of "constructive engagement" with South Africa amounted to little more than "letting the South African government go and do what it feels like doing.

"We feel we had to do something . . . ," she said. "If there was a government in Washington that looked like it was going to use its pressure, even diplomatically, on the government of Pretoria, we wouldn't have been here tonight."

Norton said civil rights leaders from around the country are planning to meet here next week to discuss further actions against the South African government.

It was the second time that Fauntroy, 51, has been arrested during the 13 years he has served as the District's nonvoting delegate to the House of Representatives. Two years ago, he was arrested while protesting the opening of a toxic waste dump in North Carolina.

D.C. Mayor Marion Barry, who said he did not know in advance of the protest, visited with Fauntroy, Berry and Robinson at the police substation.

"I am sympathetic with their protest against the apartheid system of South Africa," the mayor said. "My heart and mind and soul is with them."

Norton said she and the other three had gone to the embassy with the idea that they would be arrested if the South Africans decided to exercise that option.

Swanepoel said the embassy requested police assistance in removing the three protesters, but did not request that charges be placed against them.

Fourie, in a statement released by Swanepoel, said Fauntroy, Berry and Robinson also had demanded the release of three South African black political leaders who have taken refuge in the British consulate in Durban.

The three were sought for allegedly seeking to intimidate South Africans into not participating in recent elections there in which minorities of mixed-race and Asian origin were given a subordinate form of parliamentary representation in the white-controlled government.

But African blacks, who make up 73 percent of the population, were excluded from any role under South Africa's apartheid segregationist system.

While some leaders in the mixed-race and Asian communities welcomed the chance for increased power, others urged a boycott of the election. It succeeded to the extent that 70 percent of the mixed race and 80 percent of the Asians chose not to vote.

Police subsequently detained dozens of the boycott leaders. But the arrests generated a series of protests, which in turn drew tough official countermeasures.

This month, a number of black labor unions staged a two-day work strike, but the government responded by arresting at least 13 labor leaders, all of them black.

Asked whether the South African government intends to drop charges against the three black leaders in the British consulate, Swanepoel said, "I would assume that was denied."

Cecelie Counts, one of the demonstrators who marched near the embassy while the sit-in took place, said yesterday's action was part of an expanding approach to advocating social and political justice in South Africa.

"I think it's clear that we've just had enough," said Counts, a member of TransAfrica. "We just can't take any more."

She said the sit-in came only after detractors of the South African government had attempted less dramatic methods of protests, including letter-writing campaigns, intensive congressional lobbying and urging U.S. corporations to divest their interests in the white minority-ruled nation.

"All the people are asking for is one man, one vote," she said of the black South Africans, "the most basic principle of democracy."